Question

M={(x,y)丨y=x²-1},N={(x,y)丨y/(x-1)=1},M∩N=?

Answer 1

y/(x-1)=1

即

y=x-1

M∩N

就是求y=x²-1和y=x-1的交点

x²-1=x-1

(x+1)(x-1)=x-1

又x-1在分母上,x-1≠0

两边同时除以x-1,得

x+1=1

x=0

y=x-1=-1

M∩N={(0,-1)}

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